Brush



H. L. COOKE Dec. 29, v 1936.

BRUSH Original Filed March 2, 1934 INVENTOR H-L-CUDKE HIS ATTORNEYS- Patented Dec. 29, 1936 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to the manufacture of brushes made with bristles, and its objects are to improve the usefulness, wearing qualities, and appearance of such brushes.

While the invention is applicable to bristle brushes generally, it finds a particular'field of usefulness as applied to tooth brushes, and it is an important object of the invention to produce a tooth brush which, while effective for cleaning the teeth, cannot injure the gums. It is now recognized by leading authorities that what is ordinarily termed brushing the teeth should also include the use of the brush to massage the gums so as to promote the circulation therein and assist in maintaining the gums in a healthy condition in which they will resist disease. It is an object of my invention to provide a tooth brush which permits its use for more efiective gum massage than has been possible with ordinary tooth brushes without danger of injury to the gums or discomfort to the user.

In tooth brushes and other bristle brushes as commonly manufactured, the bristles are cutofi to the shape of the brush by some form of cutting knife. This cutting operation leaves the tips of the bristles rough and jagged and frequently with chisel-like points. In some instances the tips of the bristles split, and when the brush is used the incipient cracks or splits in the ends of the bristles will rapidly open to a point where the bristles lose their usefulness. The sharp, chisel shaped points of tooth brush bristles, especially when the brush is new, tend to abrade or scratch the gums, thereby producing a condition in which the gums are particularly susceptible to. attack by bacteria. When the brush has been used for a time the sharp pointsof the bristles absorb moisture and become soft so that they bend over and are ineffectual for cleaning the teeth. Bristles with jagged or split ends also catch and retainparticles of food or other foreign matter which may contain bacteria, and thereby whiletending to actually scratch or abrade the gumtissue'may also carry a source of infection directly into con tact with the abraded surfaces.

The objects of the invention are accomplished by properly grinding'or shaping the ends of the bristles to a smooth and usually rounded form. I have found that in grinding the ends of the bristles it is veryimportant to avoid side grinding or tapering of the bristles, it being necessary to grind thebristlesin such away that only the tip ends are smoothed off and rounded slightly, so that the ends shall be smooth, but the Divided and this application January 4, 1935, Serial No. 383

curvature. than a hemisphere, and it may be 5 somewhat flatter than this if properly smoothed so as to avoid sharp corners.

The optimum substantially hemispherical form of the tip need not be strictly adhered to in order to obtain the major advantages of the inm vention, but it is important that the tip be essentially short and blunt in character, that is, that it be so formed that the bending curvature of the tip portion shall not be greater than the bending curvature of the body portion of the 15 bristle when the bristle becomes flexed in use. If the tip of the bristle is reduced in section to a point where its bending rigidity is materially reduced then it will tend to bend over independently of or more sharply than the body of 20 the bristle, especially when wet, and thereby will tend to cause splitting of the bristle. Experiment shows that once splitting of the bristle is begun the usefulness of the bristle is permanently destroyed. If the tips of the bristles are so 25 shaped as to eliminate cracks and to prevent the incipence of cracks as explained above then the bristle becomes durable, and further use will enhance its smoothness and rounded character. On

the other han'dif the bristle is sharp and jagged 30 or provided with an elongated flexible taper then no amount of use will improve its condition but will simply cause rapid deterioration due to splitting.

Grinding ofthe bristles in such a way, and to 35 shell or outer sheath or'skin of the bristles which 45 is extremely thin, but finer and 'harderflin' texture and more water resistant than the interior part of the bristle. The removal of this resistant shell in the neighborhood of thetip of the bristle thereby permits the part of the bristle adjacent 5 the tip to absorb water and. become limp.

The bristles having tips formed in accordance with this invention are very efiective' for brushing as there are no jagged cornersto injure the guns in the case of a tooth brush, and owing 5 to the smooth formation of the tips of the bristles there is practically no tendency for the bristles to split in use. The firm, rounded tips of the bristles are very effective when used with an abrasive or polishing substance, such as tooth paste or powder, as they apply such an agent in the most advantageous manner to the surfaces of the teeth. A much more satisfactory action of the powder or paste is thus secured than in the case of a brush having jagged or pointed bristles.-

The smooth rounded tips of the bristles also permit a vigorous massaging of the gums without danger of injury thereto or discomfort to the user. The smooth rounded ends of the bristles also provide a brush having a maximum durabilityand a superior appearance and feeling to the touch.

Bristles as used in this specification means primarily animal or vegetable bristles and their equivalents, but is not intended to comprehend metallic wires nor soft rubber fingers. The latter elements may have some uses in common with bristles but lack important characteristics and functions of bristles. Synthetic or natural substances having the structure and characteristics and the functional capacities of bristles are, of course, to be regarded as comprehended within the scope of the invention.

In the accompanying drawing which illustrates certain preferred embodiments of the invention:

Figure 1 is a side elevation of a tooth brush showing a typical arrangement of tufts of bristles, the tips of each of the bristles being rounded in accordance with the present invention.

Figure 2 is a view showing typical bristles ground in accordance with my invention.

Figure 3 is a view in side elevation showing typical hristles having jagged ends as produced by the ordinary cutting operations .now commonly used in the manufacture of tooth brushes,

and showing onebristle split as the result of use in the rough tipped condition.

Figure 4 is a view showing an incorrect method of grinding bristles by which the bristles are more or less ground off on the sides and also have sharp comers or chisel-like points.

Figure 5 is a side elevation of a tuft of bristles in a tooth brush, the bristles being graduated in length so as to formtufts having rounded ends, the tips of the individual bristles also being roundedl Referring to the drawing in detail, the bristles shown in Figure 3 are illustrative of typical bristles found in tooth brushes which have been trimmed by the usual trimming knives. bristles are usually cut off at the top on a' more or less irregular incline as shown at 3.. and the corner of the bristles which is reached last by the cutter frequently projects in a point or chisel shaped edge 3|; It will be apparent that a brush .with bristles of this shape will, when stiff. present many inshnces, a jagged end of the bristle will split so that the bristle will sooner or later have the appearance of the bristle 32. With such Such a bristle the split portions will absorb moisture and soon become soft so that the bristle is practically useless. Bristles having split or jagged ends also will retain particles of food or other foreign matter which may contain bacteria.

In accordance with my invention, I form the bristles with smooth rounded ends, such as illustrated in Figure 2. The body of the bristle 35 is untouched by the grinding means, only the end It being ground into a rounded or dome shape, which meets the substantially cylindrical body of the bristle at 31. In grinding the rounded or dome shaped ends of the bristles it is important to avoid grinding the side of the bristle beyond substantially the point 31, as such grinding tends to remove the hard outer skin of the bristle, and also to taper the bristle so that the tip will lose some of its stiffness. So long as the rounding of the bristle is confined to a curvature substantially hemispherical or less, the tip of the bristle retains its stiffness. The round tip of the bristle is of ideal shape for applying a polishing powder or paste, as in the case of a tooth brush or other polishing brush, and is also the best form for any other type of stiff bristle brush, such as a clothes brush, hair brush, nail brush or the like. There are no sharp or jagged points on the bristles which can give rise to splitting thereof, or which can injure the skin of the gums, the scalp or any delicate tissue or fabric. The ends of the bristles may be rounded byv grinding upon an abrasive surface or wheel which gives a very satisfactory finish, or if desired a polishing or buffing Operation may also be utilized which will put a high polish on the tip of the bristle. Formation of the bristle tips by grinding is advantageous as it does not impair the natural appearance of the bristle.

In ordinary brushes the bristles are mounted in tufts which are set in holes in the holder or back of the brush. For instance Figure 1 shows a tooth brush having tufts 40 of typical shape mounted in the holder II. The upper ends of the tufts may be of wedge shape with the bristles at the sides of the tuft shorter than the bristles in the middle. Ordinarily a row of three or four tufts is mounted in line transversely to the brush, the wedge shaped contour extending transversely to the axis of the brush.

Figure 5 shows a different form for the contour of the tuft. In Figure 5 the top of the tuft is arch shaped as indicated at 44. The tufts are set in rows of this contour extending transversely to the axis of the brush. In some instances it may be desirable to have a double curvature at the top of each tuft so that each tuft is of a dome shaped contour, but ordinarily this is unecessary.

In accordance with my invention each bristle in the tuft is ground so as to have a dome shaped tip of substantially the form shown in Figure 2. In the manufacture of 'a brush it is possible to grind the tips of the unmounted bristles to proper shape, and then mount them in tufts in the holder, ,but the usual manner of making brushes is to mount the tufts of bristles in the holder and then trim them to the desired contour. I prefer to follow the latter procedure and then to grind the roughly trimmed tips of the bristles. In performing this grinding operation it is important that each bristle shall be treated individually, so to speak, so as to produce a rounded curvature on the end of each bristle. In grinding the bristles of a tuft having a wedge shaped contour, as shown in Figure 1 for instance, it is not sufficient merely to bring the tips of the bristles into contact with a grinding wheel having a groove of the corresponding contour therein, as indicated at 46 in Figure 4. The effect of such a grinding operation would be to grind the ends of the bristles to a chisel shape as indicated at 41. This, it will be seen, would form the bristles with objectionable points 48, more or less similar to the points formed by the usual cutters. Furthermore, the outer sides of the bristles would be ground down too far at the point 49, so that they would be more or less tapered on one side. I overcome this difficulty by, grinding the bristles in such a way that each bristle is ground so as to have a smooth rounded tip.

Any desired means may be utilized for producing brushes having the described improved formation of bristle tip. I have found that'the desired result may be accomplished in an entirely satisfactory and eflicient manner by the novel methods and apparatus which are fully disclosed in my co-pending application for patent, Serial Number, 713,669, filed March 2, 1934, of which the present application is a division.

I claim:

1. A brush bristle having substantially cylindrical side walls extending to the tip thereof and a smooth rounded tip of substantially hemispherical shape.

2. A natural bristle for bristle brushes comprising a body portion having its normal form, character and appearance throughout its length, and terminating in a rounded tip portion devoid of sharp irregularities and incipient cracks, said tip portion being of a total height not greater than the cross-sectional radius of the body portion.

3. A tooth brush composed of tufts of animal bristles each tuft having a generally pointed or ridged shape and substantially all the bristles in each tuft comprising body portions of normal form and character throughout their lengths and terminating in smooth, rounded tip portions providing polishing or brushing end faces, the tip portions being of total height not greater than the cross-sectional radii of the body portions.

4. A brush of the character described made substantially throughout of bristles comprising body portions of normal form, character and appearance merging into smooth, blunt, rounded tip portions, the blunt and roundednature of said tip portions preserving the bending rigidity of said tip portions substantially unimpaired, as compared with the bending rigidity of said body portions.

5. A bristled brush of the character described composed principally of bristles, each having a body portion which retains its full and natural cross section to a point near the working end of the bristle, and having a working tip which is blunt and of continuous rounded form throughout and which is substantially semicircular in at least one axial section.

6. A tooth brush consisting substantially of bristles each of which comprises a body of normal form and stiffness throughout, and a short, smooth, blunt, convexly rounded working tip, the blunt tip immediately surmounting the normal body portion of the bristle so that the base of the blunt tip is the full diameter of said body portion, and the surface of said blunt tip merging smoothly into the surface of the body portion.

HEREWARD LESTER COOKE. 

